Subject: [rohc] Re-write of the RTP implementer's guide, a proposal from the authors

From: "Lars-Erik Jonsson \(LU/EAB\)" <[email-masked]>
Date: Mon, 22 May 2006 12:20:27 +0200

ROHC RTP folks,

We did a WGLC on the ROHC RTP implementer's guide in December, but
at that point we were not sure about the target category for this
document. Through discussions with the AD, it was decided to target
standards track, which made us start thinking of the document in
a slightly different way. An updated -18 version was released to
introduce RFC2119 language, and a second WGLC was issued on that
draft. There were no concrete comments on the -18 version, but we
got some more philosophical high-level comments about the draft
(see the ROHC list, February 24th) that made us think we should
give the draft some more time.

So, since then the authors have spent some time on a re-write of
the draft. It is not significantly changed, but almost all parts
have been touched in some way. The re-write is in general just
editorial, not making any formal changes. However, during the
process we did find some technical flaws that we have corrected.

The draft just submitted, revision -19, is thus a proposal from
the authors. The changes from -18 are presented below and this is
thus a call for feedback on these changes. If we can agree on
these, we will be able to consider -19 current WG consensus.

The draft (when announced) will be found at:
http://www.ietf.org/internet-drafts/draft-ietf-rohc-rtp-impl-guide-19.txt

Here are the changes made (minor pure edits omitted):

* The following line has been added to the first page heading of
  the draft:
    TO UPDATE: RFC 3095, 3241, 3843, 4019, 4362
  The RFC editor will then replace this with:
    UPDATES: RFC 3095, 3241, 3843, 4019, 4362

* The title has been changed to:
        RObust Header Compression (ROHC):
    Corrections and Clarifications to RFC 3095

* The abstract has been slightly rewritten.

* Chapter titles have been slightly changed (removed useless words).

* New formalised terminology has been introduced to clearly
  indicate incorrect or incomplete text in RFC 3095, as well
  as corrections, invalidations, and additions (see the end of
  the Introduction and Terminology chapter). This means various
  sections have also been adjusted to make use of these keywords.

* Some texts have been rewritten to be more concise and clear, e.g.
  redundant text has been removed (see the diff to review these).

* Chapter 3 now incorporates everything related to mode
  transition, also "3.2. Feedback during mode transition" 
  (new section) and "3.3. Packet decoding during mode
  transition" (previously section 8.7).

* Section 3.2. has been added, its content should speak for itself.

* In section 4.5., "TS wraparound with scaled timestamp encoding",
  the TS wraparound algorithm has been invalidated since it is
  not sufficiently specified to be implemented in an interoperable
  way, neither is it needed or useful.

* Section 5.1., "Generic extension header list" has been removed
  because RFC 3095 is in no way unclear on this. When we failed
  to understand why this ever entered the implementer's guide, we
  started to dig into the mail archive, and tracked down the
  following question as a possible starting point.
  http://www1.ietf.org/mail-archive/web/rohc/old-archive/msg03548.html
  The answer to the question can be easily and clearly found in
  RFC 3095, therefore we think the section should go away from
  this document.

* The chapter 5 subsection "RTP dynamic chain" has changed title
  and is now called "5.2. Multiple occurrences of the CC field".

* Previous section 5.4., "Compressed lists in UO-1-ID packets"
  has been merged into section 6.2., "Updating properties of
  UO-1*".

* Chapter 5 now incorporates also "5.8. Compression of AH and
  GRE sequence numbers" (previously section 8.13).

* Chapter 6 now incorporates also "6.3. Context updating
  properties for IR packets" (previously section 7.3), "6.4. RTP
  padding field (R-P) in extension 3" (previously section 8.9
  "What does "presumed zero if absent" mean on page 88?"), and
  "6.5. RTP eXtension bit (X) in dynamic part" (new section).

* Section 6.5. has been added, its content should speak for itself.

* Previous section 8.3., "Extension-3 in UO-1-ID packets" has
  been merged into section 6.2., "Updating properties of UO-1*".

* A new section 8.4., "Multiple occurrences of the M bit" has
  been added, this was missing but is similar to the CC-case.

* The security considerations have been slightly rewritten.

* Indentation has been corrected in the appendix.

Please review these changes and let us know if there are any
disagreements on them, or any questions.

BR
/L-E

-----------------------------------
Lars-Erik Jonsson, M.Sc.
Senior Research Engineer
Wireless IP Optimizations
AWARE - Advanced Wireless Algorithm Research
Ericsson Research, Corporate Unit
Ericsson AB
Box 920, S-971 28 Luleå, Sweden
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